1. Field of the Invention
The present invention relates generally to the field of home safety devices for children, and more specifically to a locking device which can be placed over the male terminals of an electric appliance cord plug to prevent children and others from inserting the terminals into an outlet.
2. Description of the Prior Art
There have long been devices for preventing the unauthorized use of appliances, in the form of locks for their electric cord plugs. Such devices have chiefly been intended to protect children. The existing designs present various disadvantages including awkwardness, bulk, needless complexity, needless expense and the potential for damaging the plug terminals.
Rockman, U.S. Pat. No. 2,643,787, issued on Jun. 30, 1953, discloses a lockable container for an electrical plug to prevent its unauthorized use. The plug fits into an open side of a small box and the cord fits into a slot in an adjacent side. Then the box slides into a sleeve which covers most of the open side of the box. The box is removably locked into the sleeve with a conventional trunk-type lock. A problem with Rockman is that the device has more than one separate part, which multiples the chances of loosing an essential part. Also, the need to manipulate the separate parts makes the use more complicated and frustrating where speed is needed. Finally, since the plug end is free to rattle inside the box, the terminals are potentially subject to damage.
Laff, U.S. Pat. No. 3,524,029, issued on Aug. 11, 1970, teaches a chamber for containing a cord plug, the chamber having an interior socket for receiving the plug terminals. Wiring from the interior socket passes through a switch, which is operated by a key from outside the chamber, and the wiring then exits the chamber and ends in a plug with terminals. Thus, to deliver power to the appliance or other item, one must insert the device plug into an electric wall socket and insert and turn the key. A problem with Laff is that children can still play with exposed device terminals, inserting them into a wall socket, and possibly shocking themselves. An since the device remains attached to the cord even when power is drawn, it can be cumbersome. Laff is also a relatively complex and expensive structure for the purpose intended.
Sherman, U.S. Pat. No. 4,167,658, issued on Sep. 11, 1979, is essentially a small, updated version of Laff. Sherman is a casing with holes for receiving plug terminals. The terminals are locked into the casing holes, and a second set of terminals on the device itself plug into a wall socket. A switch on the casing operated by a key regulates the flow of current into the plug through the device. Since Sherman remains attached to the plug even when in use, it is cumbersome like Laff.
Pfenning, U.S. Pat. No. 4,488,764, issued on Dec. 18, 1984, discloses a lockable container similar to Rockman for enclosing a plug. Rather than having a box slide into a sleeve, the Pfenning container has a removable top with a key lock. Like Rockman, the need to manipulate more than one part, i.e., the box and separate locking top, makes Pfenning frustrating where speed is required. Again, the chances of loosing one of the parts is multiplied. Finally, since the plug is free to rattle in the box, the terminals may be damaged.
Goebel, U.S. Pat. No. 4,705,335, issued on Nov. 10, 1987, is still another lockable container for enclosing electric cord plugs. The primary difference between Goebel and Pfenning is that Goebel is designed to retain a plurality of plugs. Goebel has a one-piece construction, but otherwise has the disadvantages of Pfenning. An additional disadvantage is that Goebel is relatively cumbersome.
Sieverman, U.S. Pat. No. 4,812,131, issued on Mar. 14, 1989, teaches a variation of the terminal receiving lock, wherein the terminals once again fit into holes in the casing of the device. A strap with an axial series of perforations fits through a slot in the casing and claw-like arms at the end of the strap fit around the body of the plug. A key-operated locking device causes a detent to slide through one of the perforations in the strap and thus locks the plug into the device A problem with Sieverman is that, like Rockman, it has two separate parts, the strap and the casing, to manipulate when attaching or removing it. Also, the claw-like arms could be pried off the plug relatively easily, thereby freeing it for unauthorized use.
Kershaw, U.S. Pat. No. 4,865,557, issued on Sep. 12, 1989, discloses still another container for enclosing the plug of an electric cord. This container is very similar to that of Pfenning except that barbed twin posts snap through holes in the cover. The device must be destroyed to remove it from the plug. A problem with Kershaw, in addition to those of Pfenning, is that it can be used only once. Thus, Kershaw is poorly suited for frequently used appliances.
It is thus an object of the present invention to provide a plug locking device wherein its elements ar inseparably combined into a single piece and which surrounds and protects each terminal of the plug.
It is another object of the present invention to provide such a device which can be securely attached and easily removed with a key to permit reuse.
It is another object of the present invention to provide such a device which permits the user to avoid contact with the current-carrying terminals of a wall socket.
It is still another object of the present invention to provide such a device which is compact and which does not remain attached to the plug or cord when not in use.
It is finally an object of the present invention to provide such a device which is durable and inexpensive.